The present invention relates in general to flashers for lamps such as lamps in automotive vehicles, and more particularly to heavy duty flashers for turn signal and emergency warning lamps for vehicles, having very heavy load capability and high reliability.
Heretofore, various types of flashers primarily adapted for use in automotive vehicles have been available on the market, including bimetal flashers, electromechanical flashers such as "fly-wheel" type flashers and motor driven flashers, various forms of electronically driven relays, and pure electronic devices. The mechanical or bimetal type automotive lamp flashing circuits typically make and break physical contact alternatively to complete and to interrupt circuits in which they are incorporated. The switches suffer from known defects such as contact pitting, dirtying, and similar problems, and thus often need replacement. Additionally, physical making and breaking of an electrical circuit can cause sparking, which can be dangerous if an accident occurs in which fuel spillage is involved or accidents involving trucks which transport volatile loads.
With the exception of the pure electronic types of flashers, some sort of mechanical switching device has usually been employed to connect the lamp load to the power source. These contacts are prone to arching, which limits the useful life of the flasher, especially when the device has to switch heavy current loads as in the case of semi-trailer trucks which on some occasion may have as many as 16 lamps connected to the flasher.
The electronic flashers presently on the market generally use bipolar transistors, which have too high a voltage drop to be certified to the present U.S. Department of Transportation specification for such devices, or if they do meet the DOT specifications, they are packaged in a large rectangular box and have a large heatsink as an integral part of the package.
An object of the present invention is the provision of a solid state flasher for turn signal and emergency warning lamps for trucks and the like, which avoids the use of relays and electromechanical devices or mechanical switching systems customarily employed in a flasher, but packages the flasher as a solid state structure capable of flashing very heavy loads with a small voltage drop, and having long term reliability. A further object of the present invention is the provision of a novel solid state heavy duty flasher for turn signal and emergency warning lamps for trucks and the like wherein the components are packaged in a typical round can similar to common bimetal flashers, but wherein no ground connection is required and the flasher may be used on both positive and negative ground systems, which are capable of handling extremely high current loads and provide a low voltage drop.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.